Rooms (audio rooms) primarily intended for playing a musical instrument such as the piano or listening to music are required not only to have sound insulating properties but also to provide great sound (acoustics). One method to create great acoustics is “sound absorption,” and conventionally, there are sound absorbing ceiling materials, sound absorbing wall materials, and wall-mounted or standing sound absorbing panels.
For example, Japanese Unexamined Patent Application Publication No. 2005-146650 (Patent Literature 1) proposes a sound absorbing structure having a plurality of Helmholtz resonators formed in studs disposed in a space in a double wall in order to absorb sounds of a specific frequency in an air layer that is present in the double wall. Specifically, Patent Literature 1 discloses that each stud is formed by a hollow tube extending in the vertical direction, a plurality of openings that open to the space in the wall are formed in a side surface of the stud, and the peripheral portion of each opening has a tubular shape protruding laterally from the remaining portion.
It is known in the field of architectural acoustics that it is effective to place a sound absorbing material in a corner(s) of a room in order to reduce acoustics trouble called booming, namely unbalanced sound due to a build-up of low-pitched sounds in the corner(s) of the room. For example, Japanese Unexamined Patent Application Publication No. 2014-141822 (Patent Literature 2) proposes a technique in which a sound absorber substantially in the shape of a triangular prism is placed in a corner of an acoustic room and a thick part of the sound absorber absorbs sounds in a low frequency range and a thin part of the sound absorber absorbs sounds in a high frequency range. Patent Literature 2 also proposes that a variable mechanism that can change the exposed area of a sound absorbing surface (front surface) of the sound absorber be added so that acoustics can be changed.